bazaar-ng news

[Martin Pool]

Hi,

Just thought I'd let you know what I've been up to today.

I wrote a delta-compressed file store based on some ideas from Matt
Mackall and other people.  This lets us keep large trees with long
history (like the kernel) without either using too much disk space or
spending a long time pulling revisions out.  This is not completely
integrated with bzr itself yet but you can see it in bzrlib/revfile.py
in the public tree, which also has some notes about how it works.  

The design is pretty simple but effective: it compresses comparably to
RCS or SCCS but with better access speed for long-lived files, despite
being pure Python. 

As one example: there are ~480 revisions of the Makefile in the bkcvs
tree, one of the most often touched files.  The CVS ,v file is 254kB and
the 'revfile' in bzr is 290kB.  The most important place for this is in
compressing the large inventory file we use to handle file renames etc.

That's enough for me for tonight.  Tomorrow I'm going to finish
integrating this and see how it compares for large trees.  I think it
will do well.

-- 
Martin

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